11 Feb
2014
11 Feb
'14
9:49 p.m.
Rob,
thank you, would be nice to get your stripboard design.
Also thanks to Tony to justify my naive attempt to check the transformer by measuring its
resistance.
I'm just checking sources to get replacement transformers. There aren't much left.
Will try to get some transformers as spares.
Andreas
Am 11.02.2014 um 22:22 schrieb Jarratt RMA
<robert.jarratt at ntlworld.com>:
Tony sent me a circuit design for a ringing tester. I converted this into a
TinyCad drawing from which I was able to create a stripboard design. If
anyone wants this I can send it to them.
Regards
Rob
On 11 February 2014 20:49, Tony Duell <ard at p850ug1.demon.co.uk> wrote:
>>
>> I measured the resistance of the flyback transformer as of four Ohms.
>> From my point of view this is a proper value.
>
> Unofrtunately DC resistance measurments on a flyback transformer tell you
> very little. A single shorted turn in that winding will not change the DC
> resistnace enough to see. A shorted turn in anotehr windign will not
> change the resistance at all. But either will extract enough energy to
> prevent the flyback from resonating, will cause the primary currnet to go
> very high and will damage the output transistor.
>
> The only useful test is a ringing test. Basically, you resonate the
> widnidng with a capacitor 9arounf 100nF IIRC), then apply pulses to it
> (the nromal way is a nopen-collect drier using a BU406 or similar
> trasnsitor) and look at the waveform on a 'scope. A good flyback will
> show many osciallations before they decay to 'invisible', a bad one will
> probably not oscillate at all.
>
> -tony
>